1. The Cell

2. The Cell Theory Cells are the basic building blocks of life
All cells come from pre-existing cells
Cells are the basic functional unit of life
Cells are the basic structural unit of life

3. Essential Tasks Obtain food and energy – metabolism
Convert energy into a form that is useable to the organism – cellular respiration
Construct and maintain the molecules that make up parts of the cell – growth & repair
Carry out chemical reactions - metabolism
Eliminate wastes - excretion
Reproduce – mitosis/meiosis
Keep instructions on how to build structures - DNA

4. Prokaryotes vs. Eukaryotes
Two basic cell types:
Prokaryotes
Eukaryotes
“single celled”
Lack a nucleus, DNA in nucleoid instead
Lack most organelles
e.g – Most Bacteria
“multi celled”
Have DNA concentrated in a nucleus
Have organelles
e.g – Plants, Animals

5. Cell Wall + Cell Membrane Cell Membrane
Cytoplasm
Cytoplasm
Cell Wall
Cell Membrane
Nucleus
Nucleus
Centriole
Vacuole
Vacuole
Chloroplast
Green Plant Cell
Animal Cell
Outside Covering
Cell Wall + Cell Membrane
Cell Membrane
Vacuoles
Large Central Vacuole
Small random vacuole
Chloroplasts
Present
Absent
Centrioles

6. The Cell Membrane

7. Cell Membrane Function
1) Transportation of Materials
- Transport raw materials into the cell from the surrounding Extra Cellular Fluid (ECF)
e.g – O2,H2O,glucose,aa
- Transport manufactured products and wastes out of the cell into the ECF
e.g. – hormones, enzymes, CO2

8. Cell Membrane Functions
2) Gatekeeper for the Cell
- Prevent entry of unwanted matter into the cell
e.g. – bacteria, poisons
- Prevents the escape of matter needed within the cell to perform cellular functions
e.g. – keep cell parts, needed enzymes, nutrients inside cell

9. Composition of the Cell Membrane
CM is composed of 1) Lipids
2) Proteins
3) Carbohydrates

10. Phospholipids
CM is essentially a double layer (bilayer) of phospholipids
Phospholipids resemble triglycerides in structure, except that one of the 3 fatty acids has been replaced with a polar phosphate/nitrogen chain

11. Polar
Head
P/N
group
Glycerol Backbone
Glycerol Backbone
Fatty Acid Chain
Fatty Acid Chain
Fatty Acid Chain
Fatty Acid Chain
Fatty Acid Chain

12. Polar Head
- hydrophilic
- P/N chain
Non polar Tail
- hydrophobic
- FA chains

13. The dual nature of the phospholipid molecule, the cell membrane is formed of a double later of these molecules, arranged “tail-to-tail” = phospholipid bilayer
Head
Tails
Head

14. The polar head of the phospholipid is attracted to water (which is also polar)
Soluble in water
This part of the molecule is said to be hydrophilic (water-loving)
The non-polar tail of the phospholipid is not attracted to water
Not soluble in water
This part of the molecule is said to be hydrophobic (water-hating) and will avoid contact with water at all costs

15. Hydrophobic tails face inward to form the interior of the membrane (avoid contact with water)
Hydrophilic heads face outward to form the inner and outer surface of the membrane (wanted contact with water)
This phospholipid bilayer forms the backbone of the cell membrane, throughout which other macromolecules are scattered

16. Proteins
Various shapes and sizes, depending on function in the membrane
2 main kinds:
1) Peripheral Proteins – on the surface
2) Integral Proteins – through the membrane

17. Peripheral Proteins Hydrophilic (water-loving)
Are attached to inner and outer surface of membrane
In contact wit hydrophilic heads of phospholipids and watery interior/exterior of cell

18. Integral Proteins Have both hydrophilic and hydrophobic areas
Penetrate completely through or partially into the phospholipid bilayer
Hydrophobic areas contact watery interior & exterior of cell
Hydrophobic areas are embedded inside the bilayer to avoid contact with water

19. Carbohydrates Polar – hydrophilic
Found attached to outer surface of membrane only
Carbohydrate + protein = glycoprotein
Carbohydrate + lipid = glycolipid

20. Cholesterol
Allows the cell membrane to remain more rigid at high temperatures
Makes the membrane more fluid at low temperatures
Ensures that the membrane is less permeable to biological molecules
Only present in animal cells, plants have a different molecule that achieves the same functionality